Examples of known molding systems are the: (i) HyPET™ Molding System, (ii) Quadloc™ Molding System, (iii) Hylectric™ Molding System, and (iv) HyMet™ Molding System, all manufactured by Husky Injection Molding Systems Limited (Location: Bolton, Ontario, Canada; WWW-URL: www.husky.ca).
U.S. Pat. No. 3,863,001 (Inventor: Thumudo; Published: 1975 Jan. 28) discloses an improvement in a method of making a generally flat circular transfer preform from a polymeric extrudate. The method includes steps (a), (b) and (c). Step (a) includes an improved breaker plate that has oppositely disposed surfaces, and each of the surfaces generally defines a portion of a sphere, a center of curvature and a radius of curvature. The centers of curvature are both located on the upstream side of the breaker plate. The plate defines a plurality of orifices that extend through the plate and cover a major portion of the surface area of the plate. The orifices nearer the center of the plate are longer than those nearer the periphery, to compensate for the frictional drag exerted on the extrudate by the surface of the barrel. Step (b) includes forcing the extrudate through the improved breaker plate thereby forming a plurality of individual extrusions. Step (c) includes permitting the individual extrusions to nest together.
U.S. Pat. No. 3,969,055 (Inventor: Buckethal; Published: 1976 Jul. 13) discloses a system and method for controlling the injection of material through two or more gates into the cavity of injection-molding apparatus. In this system, a sensor develops an indication of unbalanced flow conditions produced by the injection of the material into the cavity of the mold. A regulator also forms part of the system and serves to adjust the relative amounts of material passing through the gates. The method includes sensing unbalanced flow conditions produced by the material injected into the cavity and adjusting the relative amounts of materials injected into the cavity through the various gates.
U.S. Pat. No. 4,965,028 (Inventor: Maus et al; Published: 1990 Oct. 23) discloses a method for improving a thermoplastic's melt quality and increasing melt temperature entering a gate of each cavity of a multicavity mold and thereby improving molded part quality. The improvement is achieved by steps (a), (b), (c) and (d). Step (a) includes injecting a plasticated melt under pressure through a nozzle seated in a sprue bushing into a multicavity moldset, melt-delivery system. The delivery system includes melt passageways maintained continuously in fluid communication between the sprue bushing on an upstream end. Runner bushings feed into each mold cavity on a downstream end. The melt contained in the delivery system is intermittently pressurized and depressurized with each injection cycle. The melt always retains sufficient fluidity to flow as required when next pressurized. Step (b) includes displacing the melt contained in the delivery system downstream toward the mold cavities. Upon each cycle's melt pressurization, the melt must pass through en route melt conditioning elements located upstream of each gate and downstream of each melt passageway. Each conditioning element consists of a male device member. The male device is generally torpedo shaped, and housed concentrically within a generally cylindrically shaped female bushing member. The conditioning element also includes a precisely dimensioned annular clearance space between the male and female members. Each conditioning element defines at least one inlet melt channel which is substantially blocked at its downstream end and at least one outlet melt channel which is substantially blocked at its upstream end. The inlet and outlet melt channels are maintained in fluid communication through the precisely dimensioned clearance space, such that melt transferring between the inlet and outlet melt channels must pass over the constrictive land. Furthermore, the melt transferring therebetween must undergo substantial angular change in flow direction as the inlet and outlet melt channels are not coaxially aligned. Each melt conditioning element feeds the melt directly into the gate. Step (c) includes shearing the melt as it flows during the intermittent pressurization of each cycle, thereby increasing the melt temperature and mixing the melt by angular flow direction change as the melt is transferred through the melt conditioning elements. Step (d) includes heating at least one of the male and female members of each melt conditioning element to a temperature greater than a temperature of the melt measured upstream of the melt conditioning elements. Forcing intimate contact between the melt and the heated members thereby increasing heat transfer between the melt and the heated members and increasing melt temperature downstream of the melt conditioning elements. This results in the melt entering each mold cavity to have substantially greater homogeneity, fluidity, and heat content with very minimally increased heat history.
U.S. Pat. No. 5,069,403 (Inventors: Marentic and Morris; Published: 1991 Dec. 03) discloses a method for providing a drag reduction article. The method includes three steps: (a), (b) and (c). Step (a) includes applying a layer of a first radiation curable composition to a carrier. Step (b) includes forming a first patterned surface on the radiation curable composition. Step (c) includes curing the first radiation curable composition by exposure to activating radiation to provide a first cured patterned surface that is capable of reducing drag resistance (that is, when a fluid flows thereacross).
U.S. Pat. No. 5,192,556 (Inventor: Schmidt; Published: 1993 Mar. 09) discloses a plastic molding apparatus for delivering a melt stream of moldable plastic material under pressure through a flow passageway and into a mold cavity. The apparatus includes a distributing plate having a distribution channel for conveying a plastic melt. A nozzle has a nozzle channel that communicates with the distribution channel. A mold cavity communicates with the nozzle channel. The mold cavity includes a connecting channel that connects the distribution channel with the nozzle channel. The connecting channel includes a flow entry portion, a reservoir portion and a flow restriction portion. The melt flows from the distribution channel to the flow entry portion, to the reservoir portion, to the flow restriction portion, and to the nozzle channel. The flow entry portion comprises a varying height channel that distributes the melt substantially equally. The reservoir portion has a larger capacity than the flow restriction portion so that the flow restriction portion holds back the melt flow from the reservoir portion. The connecting channel substantially equalizes flow pressure and flow velocity of the plastic melt to the nozzle channel.
U.S. Pat. No. 5,421,715 (Inventor: Hofstetter et al; Published: 1995 Jun. 06) discloses an apparatus for the simultaneous production of preforms, consisting of polyethylene terephthalate (PET) fed and distributed to a plurality of cavities. In order to reduce the occurrence of acetaldehyde formation in a cavity, for example, a heated distributor block used in the production of preforms of the PET material, the material flowing through a channel is subjected to additional turbulence. To this end, an element, preferably of metal, is installed in the channels, such element being provided with sets of radial spokes which are azimuthally offset in relation to each other in the axial direction. Besides inducing turbulence, such spokes act as homogenizing elements serving to diffuse heat over the cross section of the flowing process material.
U.S. Pat. No. 5,527,499 (Inventor: Miley; Published: 1996 Jun. 18) discloses an extrusion apparatus for producing a composite profile strip. The apparatus includes an extrusion head that has flow channels extending to an extrusion die. At least two extruders feed respective components at respective different pressures into the flow channels for passage to the extrusion die. The extrusion die has a common die outlet from which the components are discharged to form the composite profile strip. Respective flow restriction devices are disposed in the flow channels between the extruders and the extrusion die. The flow restriction devices are operative to decrease a difference in pressure between the components at the extrusion die to about 250 psi (pounds-per-square inch) or less prior to the components being brought together.
U.S. Pat. No. 6,343,922 (Inventors: Kazmer and Moss; Published: 2002 Feb. 05) discloses an injection molding apparatus. The apparatus including four components: (a), (b), (c) and (d). Component (a) is a manifold that has an inlet for receiving material injected from an injection molding machine. Component (b) is a plurality of injection nozzles coupled to the manifold for distributing the material to a corresponding plurality of gates to one or more mold cavities. Component (c) is a plurality of sensors respectively coupled to each of the plurality of nozzles, each sensor to sense a condition related to the rate of material flow at a location between the inlet and the plurality of gates. The last component (d) a controller to individually control respective rates at which material flows out of each of the plurality of injection molding nozzles and into the one or more cavities based on signals the controller receives from the plurality of sensors.
U.S. Pat. No. 5,683,731 (Inventor: Deardurff et al; Published: 1997 Nov. 04) discloses a redistributing device for use with melt flow exhibiting boundary layer and centralized flow. The device includes: (i) a body including a melt flow inlet end and a plurality of melt-flow outlets, said body engaging a melt flow channel, (ii) first means in said body for distributing at least said boundary layer among said plurality of melt flow outlets, (iii) second means in said body for distributing at least said centralized flow among said plurality of melt flow outlets, wherein said body has a central opening therein defining a central flow channel in fluid communication with said outlets comprising said second means for distributing, and said first means for distributing comprises inlets leading to a plurality of diverters positioned on said body and adjacent said opening, said diverters extending from said inlet end and into fluid communication with said plurality of melt-flow outlets, andwherein the material flowing in the central channel meets the material flowing in the diverters and emerges at the outlets.
U.S. Pat. No. 5,688,462 (Inventor: Salamon et al; Published: 1997 Nov. 18) discloses, in an injection molding process for making thermoplastic articles, an in-runner static mixer that is positioned near the gate to a mold cavity to mix molten thermoplastic such that said thermoplastic exiting the in-runner static mixer is more homogeneous with respect to temperature than that entering the in-runner static mixer. Passing the more homogeneously mixed molten thermoplastic through the gate to the mold cavity and allowing said cavity to fill and thermoplastic to cool, will result in an article aesthetically superior to one made by a process where no in-runner static mixing device is employed.
U.S. patent application Ser. No. 2002/0,149,135 (Inventor: Choi et al; Published: 2002 Oct. 17) discloses a multiple cavity injection molding system. The system includes a feed source that provides flowable polymeric material at conditions suitable for producing molded products therefrom. Mold cavities are adapted to receive flowable polymeric material from the feed source and produce molded products. A primary sprue extends from the feed source. A runner system extends between and providing fluid communication between the primary sprue and the plurality of mold cavities. The runner system has a feed inlet in communication with the primary sprue and a plurality of discharge ports in communication with the mold cavities. The runner system has a symmetrical configuration with respect to the primary sprue. The runner system includes at least two turbulence-inducing components. The turbulence components are selected from the group consisting of turbulence-inducing runners, turbulence-inducing steps, and turbulence-inducing angles. Upon performing an injection molding operation, the shear rate of polymeric material exiting the runner system is at least 50% of the shear rate of the polymeric material entering the runner system at the feed inlet.
U.S. Pat. No. 6,382,528 (Inventor: Bouti; Published: 2002 May 07) discloses, in an injection molding machine, a mixer that reduces the flow imbalances inherent in the melt as the flow branches within a manifold or other part of the injection machine. The mixer increase melt homogeneity by gradually mixing and changing the melt flow from all helical flow to all annular flow. The mixer provides an improved means for reducing flow imbalances that results in the elimination of weld lines and other part non-uniformities.
U.S. Pat. No. 6,544,028 (Inventor Wright et al; Published: 2003 Apr. 08) discloses a mixer method and apparatus for use generally in injection molding machines. The apparatus and method is generally comprised of a mixer insert that retains a mixing element that is sealingly inserted in the injection molding machine, for example a hot runner manifold. The mixing element reduces the melt imbalances in a flowing melt stream for the formation of improved molded parts.
U.S. Pat. No. 6,572,361 (Inventor: Gould et al; Published: 2003 Jun. 03) discloses a hot runner subsystem for an injection molding machine. The hot runner subsystem includes (i) a heated manifold having at least one primary melt channel disposed therein, (ii) an adapter plate rigidly affixed to said manifold, said adapter plate having at least one first melt channel communicating with said at least one primary melt channel, and (iii) a mixer having an inlet and an exit, said inlet communicating with said first melt channel, and said exit communicating with a secondary melt channel.
U.S. Pat. No. 6,575,729 (Inventor: Godwin et al; Published: 2003 Jun. 10) discloses a heater for an injection molding runner nozzle. The heater includes a cylindrical, heat-conducting band substrate adapted to be placed over an outer surface of the nozzle. A first dielectric layer directly is deposited on an outer cylindrical surface of the band. A conductive-ink resistive heating element is directly deposited on the first dielectric layer. The heating element is formed in a pattern to apply heat through the band to the nozzle. The heating element has first and second ends. Each end has an electrical terminal. A second dielectric layer is directly deposited over the heating element, but not over the terminals.
U.S. Pat. No. 6,923,638 (Inventor: Chen; Published: 2005 Aug. 02) discloses a hot melt distribution manifold. The manifold includes a body and a main runner. The main runner is located in the body. The body has an inlet for receiving hot melt from a source of supply. A plurality of branches located in the body has intersections with the main runner at spaced locations along its length so that at least certain intersections are farther away from the inlet than others. A plurality of nozzle assemblies is located on the body and the nozzles communicate with the branches. Selectively-adjustable restrictor devices are associated with a plurality of the branches for adjustably constricting the space available for melt flow. The restrictor devices are located upstream from the corresponding nozzle assembly in spaced relation. Each of the restrictor devices are devoid of structure projecting from the restrictor device into the corresponding nozzle assembly.
U.S. patent application Ser. No. 2004/0130062 (Inventor: Sicilia; Published: 2004 Jul. 08) discloses a mixing device for use with a manifold in an injection molding apparatus. The mixing device includes a body having a melt channel therethrough. The melt channel has a plurality of increasing sections which have an increasing cross-sectional area in a downstream direction. A plurality of decreasing sections have a decreasing cross-sectional area in a downstream direction, and the increasing and decreasing sections alternating with each other.
U.S. patent application Ser. No. 2004/0256768A1 (Inventor: Olaru; Published: 2004 Dec. 23) discloses a stack injection molding apparatus that includes a melt homogenizing element provided between a first transfer nozzle, which is coupled to a melt source, and a second transfer nozzle, which is coupled to a manifold. The melt homogenizing element is used for redistributing a melt stream in order to provide a homogenized melt stream having a generally uniform temperature and viscosity profile or sectional distribution.
Known hot-runner balancing techniques appear to include geometric and/or thermal balancing of molding material channels leading into a mold cavity of a mold. These techniques have problems associate with them. Geometric balancing is used to maintain equal pressures across all drops of the hot runner. Flow control may be achieved in two ways by: (i) making the molding material travel a longer distance before it reaches the nozzle tip, or (ii) by opening a restriction near the nozzle tip (which would increase the flow out of the nozzle for the same inlet pressure).